Phase II: The purpose of this investigation was to examine the effects of chronic hormone replacement therapy on maximal skin vascular conductance. We measured forearm blood flow and mean arterial pressure in three groups of post menopausal women at rest and during one hour of local heating (42 degrees C) of the forearm. Maximal skin vascular conductance was not significantly different among three groups of postmenopausal women. This phase was completed in January, 1997.Phase III: The purpose of this study is to investigate whether cytokines are responsible for the thermoregulatory and skin blood flow effects of hormone replacement therapy (HRT), both estrogen replacement therapy (ERT) and estrogen plus progesterone therapy (E+P), in post menopausal women. Three groups of postmenopausal women -- 9 not taking HRT, 9 E+P, and 8 ERT -- were recruited and underwent two experimental trials consisting of a whole body heating period. Each women received aspirin or placebo for three days prior to her trial. We hypothesized that if cytokines play a major role in the thermoregulatory alterations associated with hormone replacement therapy in postmenopausal women, then aspirin will normalize any differences between the three groups. Four more experimental trials are necessary for completion of Phase III. We expect to complete this phase by April, 1998.